Current Internet Protocol (IP) technology and mobile IP technology enables a host terminal or host node which is normally connected in a particular network (the node's ‘home’ network) to temporarily connect into a different network (a ‘foreign’ network) and still receive IP packets or messages sent to the host terminal at its address in the home network. Such a host terminal, which changes its point of network attachment, is known as a mobile node.
To still receive IP packets in the foreign network the mobile node must register with a so-called ‘home agent’ in its home network. In registering with its home agent, the mobile node provides the home agent with a ‘care-of’ address where it can be addressed in the foreign network. The home agent then monitors traffic in the home network, and if the home agent identifies an IP packet that is carrying a destination address corresponding to the mobile node's home address in the home network, it intercepts the IP packet. The home agent then ‘re-packages’ the IP packet and sends it to the node at the ‘care-of’ address in the foreign network.
The ‘care-of’ address may be a co-located care-of address or a foreign agent care-of address.
The technique of directing an IP packet, destined for an address in the home network, to a ‘care-of’ address in the foreign network is known, in mobile IP, as ‘tunneling’. It is important in tunneling the IP packet to the ‘care-of’ address that certain information concerning the original IP packet is retained in the re-packaged IP packet. For example, as well as maintaining the original payload (or information portion) of the IP packet, the mobile node at the ‘care-of’ address must still be able to identify in the ‘re-packaged’ IP packet the source address from which the IP packet was originally sent and the home address of the mobile node in the home network.
One technique known in mobile IP for ‘tunneling’ an IP packet to a mobile node ‘care-of’ address encapsulates the original IP packet into a new IP packet as the IP packet payload. That is the original IP packet is incorporated as the payload (or information portion) of the new IP packet without any change to its content. The ‘care-of’ address is added to the new IP packet as the new destination address and the source address of the new IP packet is identified as the home agent. On receipt the mobile node at the ‘care-of’ address removes the ‘wrapping’ on the new IP packet to recover the original IP packet.
One disadvantage with this technique is that the repackaged IP packet does not facilitate the support of quality of service provisions in conformance with existing IP quality of service standards.
Each IP packet has associated therewith, and included in the IP packet, flow identification information that identifies the quality of service associated with the IP packet transmission. This flow identification information is present in fixed locations of the IP packet, where quality of service (QoS) capable routing/switching elements can locate it and operate in dependence on it. However, with the encapsulation tunneling technique the flow identification information included in the IP packet by the source originating the IP packet is not available between the home agent and the ‘care-of’ address.
Thus the encapsulation technique in conventional mobile IP (one of which is known as IP-in-IP encapsulation) shields the real source address (i.e. the address of the correspondent node) and real destination address (i.e. the mobile node's home address), as well as the protocol ID in the IP packets, from the home agent to the mobile node. In addition, encapsulation mobile IP also changes the payload infrastructure (the original IP header becomes part of the payload) and fails flow differentiation if routers are not changed accordingly so as to be able to detect the modifications or changes. Changes or even slight modifications of routers often require a large amount of re-design and re-placement of all existing routers. This far more complicates the control and management of the networks. It may also cause problems in terms of security control and inter-operability.
The quality of service (QoS) provisions proposed to be used in the Internet are defined by standards, and in IP one known standard for quality of service signaling is called Resource Reservation Protocol (RSVP). RSVP is used in the Integrated Services Model (IntServe) quality of service framework defined by IETF. The Integrated Services Model was designed to provide special handling for certain types of traffic, provide mechanisms for applications to choose between multiple levels of delivery services for its traffic, and to provide signaling for quality of service parameters at Layer 3 in the OSI RM (signaling at layer 2 in ATM).
IntServe defines two classes of services. The Controlled Load Class provides traffic delivery in the same way as when the network is unloaded (“better than best delivery”). The Guaranteed QoS Service Class delivers traffic for applications with a bandwidth guarantee and delay bound.IntServe requires QoS capable nodes and a signaling protocol to communicate QoS requirements between applications and nodes and between nodes.
RSVP is the QoS signaling protocol used by IntServe. RSVP provides receiver QoS requests to all router nodes along the transit Path of the traffic, maintains the soft-state (Path/Reservation states), and results in resources being reserved in each router.
For RSVP/IntServe quality of service to operate, the flow identification information must be in a fixed location in the IP packets. An RSVP session is configured by the host terminals exchanging so-called Path and Reservation messages prior to data transmission.
To enable the quality of service control across the transit path between peer host terminals, each host terminal must therefore have the functionality to configure the necessary messages and recognize quality of service requests corresponding to an RSVP session.
Existing RSVP does not specify how to specifically process Path and Reservation (Resv) messages in the scenario of mobility control based on mobile IP. Moreover, the ‘tunneling’ of standard mobile IP (e.g. IP-in-IP encapsulation) disables the correct flow identification and classes of service differentiation.
It is therefore an object of the present invention to provide a technique which enables the quality of service requirement determined by the source of the message to be supported throughout the routing of the message to a mobile node's ‘care-of’ address.